Adaptive Gain Equalizer and Modulation Frequency Domain for Noise Reduction

Sammanfattning: Speech quality during the communication is generally e ected by the surrounding noise and interference. To improve the quality of speech signals and to reduce the amount of disturbing noise, speech enhancement is one of the emerging and most used branches of signal processing. For the reduction of noise from speech signals, methods are continuously developed, one method is the Adaptive Gain Equalizer (AGE) which is a single-channel speech enhancement, method that has the particular focus on enhancement of speech instead suppression of noise. Modulation decomposition of the speech signals brought the idea of a modulation system which is useful for modeling of speech and other signals. The purpose of this thesis is to implement the AGE within modulation system, for the purpose of enhancing speech signal, by reducing noise. The successful implementation of the system has been validated with di erent performance measurements, i.e., Signal to Noise Ratio Improvement(SNRI), Mean Opinion Score(MOS), Spectral Distortion(SD). The system has been checked with male and female speaker and with the noise signals Engine Noise(EN), Factory Noise(FN), Gaussian Noise(GN), Tonal Noise(TN) and Impulse Noise(IN) at 0dB, 5dB, 10dB and -5dB Signal to Noise Ratio(SNR). The system has provided the 10dB SNRI for the TN, and around 6dB SNRI for EN and FN. The system has some compromises on the GN and IN in a sense it gives good sound but low SNRI. MOS has been shown between 4 and 3 for all the test cases.